Question 334097
let son be x years
dad = 7x
..

10 years later
son = x+10 years
dad = 7x +10 years
..
7x+10=3(x+10)
7x+10=3x+30
7x-3x=30-10
4x = 20
x= 5
son's age now = 5 years
dad's age now = 7*5 = 35 years
..